Energy storage systems (ESS) are growing in importance as renewable energy sources like wind power, wave power and solar are being commissioned and connected to the grid at an ever-increasing rate. Energy Storage Systems are needed to help the grid deal with the instability and unpredictability of such power generation systems and match them to equally variable consumer demand. In the UK, renewables currently produce over 20% of the country’s electricity and this is likely to exceed 30% by 2020. The current installed capacity is in the region of nine gigawatts indicating the nation’s reliance on more environmentally friendly forms of energy generation into the future. Battery-based systems are rapidly gaining market share for use as ESSs and gaining acceptance due to advances in their design. Other energy storage approaches can use a range of media, including compressed ai...